Method of resin-sealing and molding an optical device

ABSTRACT

There is provided a method of sealing and molding an optical device with resin by employing a die including a top piece, a bottom piece, an intermediate piece, and a mold release film pinched between the bottom and intermediate pieces and thus tensioned as prescribed to cover the bottom piece&#39;s cavity, when the bottom piece is heated, and the mold release film expands and thus closely contacts the cavity&#39;s entire surface along the cavity&#39;s geometry so that the optical device can be sealed in transparent set resin shaped as desired.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to methods of sealing and molding withresin an optical device serving as a part of an optical electroniccomponent.

2. Description of the Background Art

Conventionally, for example as disclosed in Japanese Patent Laying-OpenNo. 61-1067, a 2-piece transfer molding die has been employed to seal anoptical device with resin to produce an optical electronic component (ora molded product). The optical device thus sealed with resin is forexample a light emitting diode (LED) mounted on a substrate. This LEDchip is sealed with transparent resin acting as a lens. Employing such a2-piece transfer molding die causes a problem depending on thetransparent resin's properties, as follows:

The aforementioned transparent resin melts as the die is entirelyheated. The melted resin is significantly low in viscosity andaccordingly easily leaks out the die's cavity, resulting in resin flash.

Furthermore, the die has a path (e.g., a cull, a runner, a gate, a sprueor the like) to introduce the transparent resin into the cavity. As aresult, the resin sealing the optical device and that present in thepath would set in one piece.

Furthermore, the set resin at high temperature is small in hardness. Assuch, the set resin tends to adhere on the cavity's molding surface. Assuch, if the set resin is in contact with a molding surface having acurved surface corresponding to that configuring a lens, it is difficultto remove the set resin from the cavity's molding surface. Furthermore,if the lens is successfully removed from the die's molding surface, thelens tends to have a surface with protrusion and depression. As such, itis difficult to provide the lens with a mirror finished surface.

Furthermore, if the lens has voids formed therein, the lens unevenlytransmits light, resulting in uneven brightness. This impairs theoptical electronic component (or product) in quality.

Accordingly, the present inventors have been studying a method employinga transferless molding die, rather than the aforementioned transfermolding die, i.e., a die free of a resin path and thus reducingunnecessary resin to seal a product with resin. This method employs amold release film to provide enhanced releasability between the die andthe transparent resin and that between the optical electronic componentand the die. Furthermore, the die's cavity is defined by a spacevacuumed to prevent voids caused while the transparent resin is heatedand melted.

Hereinafter the aforementioned method of sealing and thus molding withresin will more specifically be described.

The above described method employs a matrix substrate with a largenumber of surface mounted optical devices mounted thereon. Furthermore,this method employs a die composed of three pieces (i.e., a top piece, abottom piece and an intermediate piece) and a mold release film.Furthermore, the die has an internal space vacuumed. This method cansolve a problem that has not been overcome by a conventional 2-piece,transferless molding die, as disclosed in Japanese Patent Laying-OpenNo. 2004-98364. More specifically, it can prevent the mold release filmfrom wrinkling. This is because the bottom and intermediate pieces cansandwich and thus tension the mold release film.

The 3-piece die disclosed in Japanese Patent Laying-Open No. 2004-98364,however, cannot cover the entire surface of the cavity of the bottompiece with the mold release film. Furthermore, if the cavity's moldingsurface is a curved surface, the curved surface cannot be appropriatelycovered with the mold release film. As a result, the optical devicecannot be sealed in transparent resin shaped as desired.

SUMMARY OF THE INVENTION

The present invention contemplates a method of sealing and thus moldingan optical device with resin that can provide an optical electroniccomponent having an optical device sealed in transparent resin shaped asdesired.

The present method employs a die including a first piece, a second piecehaving a cavity and opposite to the first piece and a third piecearranged between the first and second pieces, and a mold release filmcovering the cavity to seal and mold an optical device in the cavitywith resin, including the steps of: attaching to the first piece asubstrate having the optical device mounted thereon; bringing the moldrelease film sandwiched between the second and third pieces into contactwith the cavity's entire surface along the cavity's geometry; closingthe first, second and third pieces together and sealing the opticaldevice in the cavity with melted resin; setting the melted resin toprovide transparent set resin; separating the first, second and thirdpieces; and removing from the first piece the substrate having theoptical device sealed in the transparent set resin.

In the present method the mold release film can be brought into contactwith the cavity's entire surface along the cavity's geometry to providean optical electronic component having an optical device sealed withtransparent set resin shaped as desired.

Furthermore in the present method the second piece may be provided withan aspiration system aspirating and thus bringing the mold release filminto contact with the cavity's entire surface to further ensure that themold release film can closely contacts the cavity's entire surface.

Furthermore in the present method air may be blown toward the moldrelease film to bring the mold release film into contact with thecavity's entire surface. This can also further ensure that the moldrelease film is brought into contact with the cavity's entire surface.

Furthermore in the present method the second piece may be heated tobring the mold release film into contact with the cavity's entiresurface. This can also further ensure that the mold release film isbrought into contact with the cavity's entire surface.

Furthermore the cavity desirably has a plurality of curved portions eachcorresponding to an optical device, and a flat portion allowing theplurality of curved portions to communicate with each other. This allowsmelted resin to flow from a curved portion retaining a large amount ofresin into that retaining a small amount of resin to allow the pluralityof curved portions to retain uniform amounts of resin, respectively.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of a substrate having a plurality of opticaldevices mounted thereon.

FIG. 2 is a cross section of an optical electronic component cut out ofthe FIG. 1 substrate.

FIG. 3 is a cross section of a die employed in a method of sealing andthus molding with resin.

FIG. 4 shows the bottom and intermediate pieces sandwiching the moldrelease film.

FIG. 5 shows an air blow system causing the mold release film contactingthe cavity'entire surface.

FIG. 6 shows the cavity's entire surface with the mold release film incontact therewith.

FIG. 7 shows the cavity receiving resin.

FIG. 8 shows a substrate and a resin material supplied in the die.

FIG. 9 shows the die vacuumed.

FIG. 10 shows an optical device immersed in melted resin.

FIG. 11 shows the top piece and the intermediate and bottom piecescompletely close together.

FIG. 12 shows an optical electronic component removed from the bottompiece.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter with reference to the drawings the present method of sealingand thus molding an optical device with resin will be described.

In the present embodiment, the method employs an intermediate product24, as shown in FIG. 1, composed of a circular or polygonal substrate 15and a plurality of LED chips or similar optical devices 16 mounted onone surface of substrate 15. Intermediate product 24 is sealed withresin to provide an optical electronic component 28 including a sealingmold 25, the substrates periphery 26, and a surface free of mounting 27.

Sealing mold 25 is formed of transparent resin 17 heated, melted andthereafter set. It is provided on one main surface of substrate 15.Furthermore, the substrates periphery 26 is a region on one main surfaceof substrate 15 and outer than sealing mold 25. Furthermore, surface 27is the other main surface of substrate 15 that is not provided withsealing mold 25.

Furthermore, optical electronic component 28 shown in FIG. 1 is cut at aportion 29 (or along a virtual line) to provide a plurality of opticalelectronic components 30 (or products) corresponding to a plurality ofoptical devices 16, as shown in FIG. 2.

Furthermore, sealing mold 25 has a semi-spherical, curving portion 31corresponding to a lens, and a flat portion 32 parallel to the mainsurface of substrate 15 and surrounding curving portion 31.

Note that while in FIG. 1 a single optical device 16 corresponds to asingle curving portion 31, alternatively a plurality of optical devices16 may be contained in a single curving portion. Alternatively, opticaldevice 16 may be contained in a polyhedron rather than curving portion31.

Furthermore, desirably, transparent resin 17 is for example epoxy resinor silicone resin as it serves to protect optical device 16 as well asacts as a lens. Furthermore, transparent resin 17 may be resin in theform of liquid or a sheet, rather than granules.

Furthermore in the present embodiment the present method does not employa conventionally used, transfer molding die. Rather, as shown in FIG. 3,it employs a transferless molding die 1, which does not have a resinpath, i.e., it does not have a resin path wastefully providing setresin. Die 1 is a 3-piece die composed of a top piece 2, a bottom piece3 opposite top piece 2, and an intermediate piece 4 arranged between topand bottom pieces 2 and 3.

Bottom piece 3 has a protrusion 33 serving as a main body of bottompiece 3. Protrusion 33 has a surface 9 opposite top piece 2. Surface 9has a cavity surface 5 defining a cavity space. Cavity surface 5 has acurved portion 5 a corresponding to curving portion 31 of optical device16, and a flat portion 5 b corresponding to flat portion 32 of opticaldevice 16. Furthermore, bottom piece 3 can move upward and downward.Furthermore, bottom piece 3 is provided with a pinching member 12pinching mold release film 7, a cavity member 20 forming a portion ofthe cavity, and other members. Note that pinching member 12 is providedwith a through hole 37.

Intermediate piece 4 has a surface 11 opposite the bottom piece and asurface 10 opposite the top piece and can move vertically. Furthermore,between surface 11 and cavity surface 5 mold release film 7 is supplied.Furthermore, when bottom piece 3 and intermediate piece 4 are closedtogether bottom piece 3 and intermediate piece 4 coorporate to sandwichmold release film 7. Furthermore, as shown in FIG. 3, intermediate piece4 is provided with a through hole 36 extending from surface 10 tosurface 11. When intermediate piece 4 moves downward, through hole 36receives the bottom piece 3 protrusion 33 inserted therethrough, asshown in FIGS. 4-6, when the pinching member 12 through hole 37 alsoreceives protrusion 33 inserted therethrough.

Furthermore, as shown in FIG. 3, top piece 2 has a substrate bearingportion 34, a sealing member 13, and a suction and exhaust hole 35.Furthermore, top piece 2 has a surface 8 positionally fixed. Substratebearing portion 34 has attached thereon substrate 15 having opticaldevice 16 mounted thereon such that the device faces downward.Furthermore, top piece 2 has a periphery provided with sealing member13. When top piece 2 and intermediate piece 4 are closed together,sealing member 13 abuts against surface 10 of intermediate piece 4moving upward. This isolates the space in die 1 from externalatmosphere. Furthermore, suction and exhaust hole 35 providescommunication between surface 8 and a vacuuming system (not shown). Theair in the space in die 1 is aspirated by the vacuuming system and thusexternally exhausted through suction and exhaust hole 35.

Furthermore, substrate bearing portion 34 attracts and releasessubstrate 15 to and from surface 8 as an air vent having an opening insurface 8 attains negative pressure and positive pressure, respectively.Note that between substrate bearing portion 34 and sealing member 13 achuck system (not shown) may be provided to support the substratesperiphery 26.

Die 1 thus structured is used to seal and thus mold an optical devicewith resin in the present method, as will more specifically be describedhereinafter. The present method is characterized in that mold releasefilm 7 can be brought into contact with the cavity's entire surface (5and 21) along the surface's geometry.

The present method is performed as follows: initially, top piece 2,intermediate piece 4 and bottom piece 3 are separated. Then, as shown inFIG. 3, mold release film 7 is inserted between intermediate piece 4 andbottom piece 3. Subsequently, intermediate piece 4 moves downward. Thus,as shown in FIG. 4, intermediate piece 4 and pinching member 12 pinchmold release film 7.

Note that pinching member 12 has a lower surface provided with a rodmember 38. Pinching member 12 and rod member 38 are supported by aspring or similar resilient member 39 and can move upward and downward.At an opened position, as shown in FIG. 3, resilient member 39 is notcontracted, and pinching member 12 assumes its topmost position. Whenintermediate piece 4 and bottom piece 3 are closed together, pinchingmember 12 and rod member 38 move downward and resilient member 39 iscontracted.

Subsequently when intermediate piece 4 and pinching member 12 togetherpinching mold release film 7 move farther downward, then, as shown inFIG. 4, mold release film 7 abuts against the cavity member 20 topmostsurface, or a portion 40 abutting against the substrate.

Furthermore, cavity member 20 is fit into protrusion 33 having cavitysurface 5 to surround protrusion 33. Furthermore, cavity member 20 has across section in the form of the letter L composed of a vertical portionand a horizontal portion.

The cavity member 20 vertical portion includes portion 40 abuttingagainst the substrate's periphery 26 with mold release film 7interposed, the cavity's circumferential surface 22 located at acircumference of cavity surface 5, and the cavity's side surface 23connecting portion 40 and the cavity's circumferential surface 22together.

Furthermore, the cavity member 20 horizontal portion includes a topsurface bearing pinching member 12, and a bottom surface abuttingagainst surface 9 and a resilient member 41 fitted into a recessprovided in bottom piece 3.

Note that in the present embodiment the cavity member 20 cavity surface21 and the recess 33 cavity surface 5 define the cavity's entiresurface.

Then, intermediate piece 4 and the bottom piece 3 pinching member 12together pinching mold release film 7 move farther downward and die 1goes through a position as shown in FIG. 5 and then assumes that shownin FIG. 6, when the intermediate piece 4 surface 11 opposite the bottompiece is positionally lower than the cavity member 20 portion 40. Inthat condition, intermediate piece 4 and bottom piece 3 are closedtogether and the cavity's space 6 is thus formed. Furthermore, a bottomsurface of pinch member 12 and a top surface of the horizontal portionof cavity member 20 abut against each other, while a bottom surface ofthe horizontal portion of cavity member 20 and surface 9 still do notcontact each other and the cavity member 20 resilient member 41 is stillnot contracted.

Furthermore, in that condition, die 1 is heated, and mold release film 7accordingly extends. As a result, of mold release film 7, a portionlocated inner than portion 40 closely contacts the cavity's entiresurface (5 and 21). More specifically, mold release film 7, receivingheat from bottom piece 3, closely contacts curved portion 5 a and flatportion 5 b of cavity surface 5 corresponding to the lens's curvingportion 31.

Furthermore, to ensure that mold release film 7 closely contacts thecavity's entire surface (5 and 21), desirably protrusion 33 and cavitymember 20 are each provided with a film aspiration system (not shown)compulsively aspirating mold release film 7. A possible film aspirationsystem includes a large number of holes provided for each of protrusion33 and cavity member 21 and having one end communicating with cavitysurface 5 or 21, and a vacuum pump connected to the other end of thelarge number of holes. The vacuum pump can operate to attract moldrelease film 7 toward the cavity's entire surface (5 and 21) through thelarge number of holes to bring mold release film 7 into contact with thecavity's entire surface (5 and 21).

Furthermore, if the film aspiration system has a function blowing outair, then after resin sealing completes when the die is opened thesystem can blow air against sealing mold 25 (or set resin 19) via moldrelease film 7 to help to remove optical electronic component 28 fromcavity surface 5. This can eliminate the necessity of employing an ejectpin to push out the optical electronic component, as conventional.Sealing mold 25 can thus be protected from damage.

Furthermore, to bring mold release film 7 into contact with the cavity'sentire surface (5 and 21), an air blow system 42 blowing air downwardtoward mold release film 7 is desirably provided, as shown in FIG. 5.The blown air exerts pressure, which brings mold release film 7 intocontact with the cavity's entire surface (5 and 21) such that the filmdoes not wrinkle and can thus be placed along the cavity's entiresurface.

Furthermore, providing both the aforementioned film aspiration systemand air blow system 42 to die 1 can further ensure that mold releasefilm 7 is brought into further closer contact with the cavity's entiresurface (5 and 21). Note that mold release film 7 extends as it receivesheat from bottom piece 3. Accordingly, desirably, mold release film 7 isexcellent in heat resistance and durability.

Then, as shown in FIG. 7, a carrier 43 carries intermediate product 24and transparent resin 17 between top piece 2 and intermediate piece 4.Carrier 43 may carry substrate 15 and transparent resin 17 separately ortogether. Furthermore, carrier 43 may include air blow system 42.

Then, as shown in FIG. 8, intermediate product 24 has surface 27attached to substrate bearing portion 34. Note that die 1 is heated to atemperature required to melt transparent resin 17.

Attaching intermediate product 24 to surface 8, forming the cavity'sspace 6, preliminarily heating die 1 entirely, and supplying thecavity's space 6 with transparent resin 17, and the like, asaforementioned and shown in FIGS. 3-8, may be performed in any order,although they should be completed before a vacuuming step, as shown inFIG. 9 and described hereinafter.

Then, as shown in FIG. 9, the cavity's space 6 is supplied withtransparent resin 17 and bottom piece 3 and intermediate piece 4 moveupward toward top piece 2. Thus the top piece 2 sealing member 13 andthe intermediate piece 4 surface 10 opposite the top piece abut againsteach other. Thus the cavity's space 6 is isolated from externalatmosphere, and a space 14 isolated from external atmosphere is thusformed. Furthermore, substantially simultaneously, as indicated in FIG.9 by an unbroken arrow, air is compulsively exhausted through suctionand exhaust hole 35 communicating with the vacuuming system. Transparentresin 17 in the cavity's space 6 is not required to be melted when thedie assumes the FIG. 9 position: it is only required to be melted whenthe die assumes the FIG. 10 position.

While die 1 is vacuumed with the intermediate piece closed, die 1 mayalternatively be vacuumed in steps between the FIG. 9 position closingthe intermediate piece and the FIG. 10 position completely closing thedie such that the bottom piece 3 and intermediate piece 4 operation isinterrupted several times. Alternatively, die 1 may continuously bevacuumed such that rather than the bottom piece 3 and intermediate piece4 operation is interrupted, bottom piece 3 and intermediate piece 4ascend at a reduced rate after the intermediate piece is closed untilthe die is completely closed.

Then, as shown in FIG. 10, intermediate piece 4 and bottom piece 3further, together ascend and portion 40 abuts against intermediateproduct 24 periphery 26 with mold release film 7 posed therebetween,when optical device 16 is immersed into melted resin 18 in the cavity'sspace 6. Furthermore, mold release film 7, bearing the weight of meltedresin 18, is prevented from wrinkling and thus closely contacts thecavity's peripheral and side surfaces 22 and 23 and curved and flatportions 5 a and 5 b. This can provide sealing mold 25 having asatisfactory geometry corresponding to that of cavity surface 5.

Then, as shown in FIG. 11, with intermediate product 24 abutting againstportion 40, as shown in FIG. 10, bottom piece 3 has protrusion 33 alonemoving upward to allow cavity surface 5 to have flat portion 5 bsubstantially flush with the cavity's circumferential surface 22. Inthis condition, pinching member 12 and cavity member 20 abut againsteach other and the bottom surface of the horizontal portion of cavitymember 20 and surface 9 abut against each other, and resilient members39 and 41 provided in bottom piece 3 are most contracted. This conditioncorresponds to die 1 completely closed.

Note that while in the FIG. 11 position showing die 1 completely closed,the cavity surface 5 flat portion 5 b and the cavity's circumferentialsurface 22 are substantially flush with each other, alternatively, forsome amount of resin in the cavity's space 6, cavity surface 5 may haveflat portion 5 b positionally higher or lower than the cavity'scircumferential surface 22.

Furthermore, flat portion 5 b may have any depths. For example, ifcavity surface 5 does not have flat portion 5 b, curved portion 5 a mayalone be supplied with a required amount of transparent resin 17.

Furthermore, a pressure sensor or similar measurement instrument (notshown) may be buried in protrusion 33 to monitor pressure closing die 1.

Furthermore, vacuuming the die is completed between the FIG. 9 positionclosing the intermediate piece and the FIG. 10 position completelyclosing the die, although desirably, the die is continuously vacuumeduntil the FIG. 10 position is assumed or the intermediate product iscompletely sealed with resin.

Then, although not shown, melted resin 18 sets and sealing mold 25 orset resin 19 is thus provided. Thus, optical electronic component 28shown in FIG. 1, or a molded product completes.

Then, as shown in FIG. 12, top piece 2, and intermediate and bottompieces 4 and 3 are separated, and bottom piece 3 has protrusion 33 alonemoving downward. Accordingly, cavity surface 5 has flat portion 5 bmoving to be lower than the cavity's circumferential surface 22. Thisforms a gap between set resin 19 and mold release film 7 and opticalelectronic component 28 is removed from cavity surface 5. In thatcondition, top piece 2, and intermediate piece 4 and bottom piece 3 arefurther separated. Subsequently, optical electronic component 28 isremoved from top piece 2 by carrier 43. Desirably, carrier 43 has asystem cleaning the used mold release film 7 when optical electroniccomponent 28 is removed from die 1.

The method of sealing and thus molding optical device 16 with resin, asdescribed above, can achieve both an effect obtained by using moldrelease film 7 and an effect obtained by vacuuming the die, as well asbring mold release film 7 into contact with the cavity's entire surface(5 and 21).

Note that while in the present embodiment a fixed top piece 2 andvertically movable intermediate and bottom pieces 4 and 3 form die 1,top piece 2 and intermediate piece 4 may be movable and bottom piece 3may be fixed, and the role of top piece 2 and that of bottom piece 3 maybe vice versa. Furthermore, top piece 2, intermediate piece 4 and bottompiece 3 are not limited to the above described structure and may haveany structure that allows molding with resin, as described above.

Furthermore, while transparent resin 17 is composed of granular resin,it may alternatively be composed of liquid resin, powdery resin, orresin in the form of fine particles having a grain size larger thanpowdery resin and smaller than granular resin.

Furthermore, the intermediate product may be replaced with any of a wirebonding substrate with optical device 16 electrically connected tosubstrate 15 by a wire, a flip chip substrate with optical device 16electrically connected to substrate 15 by a bump, a wafer substrate, andthe like.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

1. A method employing a die including. a first piece, a second piecehaving a cavity and opposite to said first piece and a third piecearranged between said first and second pieces, and a mold release filmcovering said cavity to seal and mold an optical device in said cavitywith resin, comprising the steps of: attaching to said first piece asubstrate having said optical device mounted thereon; bringing said moldrelease film sandwiched between said second and third pieces intocontact with said cavity's entire surface along said cavity's geometry;closing said first, second and third pieces together and sealing saidoptical device in said cavity with melted resin; setting said meltedresin to provide transparent set resin; separating said first, secondand third pieces; and removing from said first piece said substratehaving said optical device sealed in said transparent set resin.
 2. Themethod according to claim 1, wherein: said second piece is provided withan attraction system; and the step of bringing brings said mold releasefilm into contact with said cavity's entire surface by suction.
 3. Themethod according to claim 1, wherein the step of bringing brings saidmold release film into contact with said cavity's entire surface byblowing air toward said mold release film.
 4. The method according toclaim 1, wherein the step of bringing brings said mold release film intocontact with said cavity's entire surface by heating said second piece.5. The method according to claim 1, wherein said cavity has a pluralityof curved portions each corresponding to an optical device, and a flatportion allowing said plurality of curved portions to communicate witheach other.